Ramsden ocular.



A 9H Qu) B-Tsval 7 nu .null rm- It.. Vinum, A c.

Lstriazi.

.UNITED STATES PATENT OFFICE.

ALBERT KNIG, OF JENA, GERMANY, ASSIGNOR TO THE FIRM OFA CARL ZEISS, 0F JENA.; GERMANY.

nAMsDN oCULan.

To all whom 'it 'may concern.'

Be it known that I, ALBERT KNIG, doctor of philosophy, a citizen of the German Emire. and residing at Carl Zeiss strasse, Jena, 1n the Grand Duchv of Saxe-Weimar, Germany, have invented a new and useful Ramsden Ocular, of which the following is a speci- I collective The invent-ion consists in an improved Ramsden ocular. In the specification 775,553 a three lens system consistincY of a double lens and a separate collectiveens has been shown by Figure 2 and described as an evelens system for Ramsden oculars, which reproduces the virtual image ro'ected by the held-lens Withoutconsi era le chro mat-icand astigmatic aberrations orl dis'- tortion. Thus in the Ramsden ocular'c'onstructed with this eye-lens system sharpness of the ima-ge has been combined with the merits of the Kellner ocular. But this suc- 'cess is accompanied by the drawback, that there are tvro highly curved surfaces to be made, viz., those cemented together. It' will be seen frointhe data given with reference to Fig. 2 in the specification cited, that in that example the radius of these surfaces amounts to little more than a third ofthe focal length of the eye-lens system. present invention a considerably smaller curvature of the two cemented surfaces is achieved by the following modification. In the eye-lens system according to specification 775.353, Fig. 2, the cemented correcting lens precedes the simple lens, on which the collective effect of the system depends, in this way, that it turns the convex side of its cement-ed 'surface to the simple lens. direction of curvature must be reverse-d, a suitable choice of the kinds of glass for the double lens being supposed. By doinff so the curvature of the cemented surface is essened. no matte-r. virhether the total effect of the double lens be collect-ive or dispersive, if it be only, relatively weak, that is at most onlv halfvso ovverful as the collective efect of the simple ens. Investigation has further revealed, that the lessening of the curva-ture of the cemented surface 1s greatest, if the order of the two lenses be reversed, that is, if the collective simple lens--to which, accord- Specication of Letters Patent.

f Application filed May 25. 1907. Serial No. 375.606.

l i l l radii, thiclmesses and distances for the lenses According to the This Patented Dec. 17, 1907 ing to the present invention, the double has to turn the concave side. of its cemented.

surface-be the front lens.

A constructional example is re. resented 5 eeld ens is'a'sim-i In the eye-lens system the sim lexf the annexed drawing. T ple one.

lens precedes the double lens. e

i em loyed in this example are here tabulated l an have referencetoan ocular having afocal lengt-h 100. The ln'nds of glass are charaeterized by the refractive indices n, and nf appertaining to thelines C and F ofthe solar 1. A Ramsden ocular, the eye-lens system of which is composed of a simple collective lens and a double lens, the components ofthe double lens being cemented together with curved surfaces concave towards the simple lens and the absolute value of the power 'of ALBERT KNIG. Witnesses:

PAUL KRGER, Farrz SANDER. 

